before, after, found := bytes.Cut([]byte(s), []byte(sep))
		fmt.Printf("Cut(%q, %q) = %q, %q, %v\n", s, sep, before, after, found)
	}
	show("Gopher", "Go")
	show("Gopher", "ph")
	show("Gopher", "er")
	show("Gopher", "Badger")
	// Output:
	// Cut("Gopher", "Go") = "", "pher", true
	// Cut("Gopher", "ph") = "Go", "er", true
	// Cut("Gopher", "er") = "Goph", "", true
	// Cut("Gopher", "Badger") = "Gopher", "", false
}

	var nonblank []string
	for i, line := range lines {
		line = strings.TrimSpace(line)
		if line == "" || strings.HasPrefix(line, "#") {
			continue
		}
		if needApproval {
			feature, approval, ok := strings.Cut(line, "#")
			if !ok {
				log.Printf("%s:%d: missing proposal approval\n", filename, i+1)
				exitCode = 1
			} else {
				_, err := strconv.Atoi(approval)
				if err != nil {

		}

		// The prefix field should never appear in the GNU format.
		var blk block
		copy(blk[:], b.Bytes())
		prefix := string(blk.toUSTAR().prefix())
		prefix, _, _ = strings.Cut(prefix, "\x00") // Truncate at the NUL terminator
		if blk.getFormat() == FormatGNU && len(prefix) > 0 && strings.HasPrefix(name, prefix) {
			t.Errorf("test %d, found prefix in GNU format: %s", i, prefix)
		}